Biden, Trump win Michigan primaries, edging closer to November rematch

US President Joe Biden and former president Donald Trump have won the Michigan primaries, further solidifying the all-but-certain rematch between the two men for the White House.

Biden defeated Minnesota Rep. Dean Phillips, his one significant opponent left in the Democratic primary. But Democrats were also closely watching the results of the "uncommitted" vote, as Michigan has become the epicentre for dissatisfied members of Biden's coalition that propelled him to victory in the state — and nationally — in 2020.

As for Trump, he has now swept the first five states on the Republican primary calendar.

His victory in Michigan over his last major primary challenger, former UN ambassador Nikki Haley, comes after the former president defeated her by 20 percentage points in her home state of South Carolina on Saturday.

The Trump campaign is looking to lock up the 1,215 delegates needed to secure the Republican nomination sometime in mid-March.

Both campaigns are watching Tuesday's results for more than just whether they won as expected.

For Biden, a large number of voters choosing "uncommitted" could mean he's in significant trouble with parts of the Democratic base in a state he can hardly afford to lose in November.

Trump, meanwhile, has underperformed with suburban voters and people with a college degree, and faces a faction within his own party that believes he broke the law in one or more of the criminal cases against him.

Biden has already sailed to wins in South Carolina, Nevada and New Hampshire.

The New Hampshire victory came via a write-in campaign as Biden did not formally appear on the ballot after the state broke the national party rules by going ahead of South Carolina, which had been designated to go first among the Democratic nominating contests.

Both the White House and Biden campaign officials have made trips to Michigan in recent weeks to talk with community leaders about the Israel's bloody war in Gaza and how Biden has approached the conflict, but those leaders, along with organisers of the "uncommitted" effort, have been undeterred.

That push, which began in earnest just a few weeks ago, has been backed by officials such as Democratic Rep. Rashida Tlaib, the first Palestinian American woman in Congress, and former Rep. Andy Levin.

Our Revolution, the organising group once tied to Sen. Bernie Sanders, I-Vt., had also urged progressive voters to choose "uncommitted", saying it would send a message to Biden to "change course NOW on Gaza or else risk losing Michigan to Trump in November."